1. Field of the Invention
The present invention relates to a lamp constructed by providing an LED (light emitting diode) chip to a reflection case having an opening at the front side thereof.
2. Description of the Related Art
A plane light emitting device for making light from a light source incident to an end face of a light guide plate and emitting light in the form of a plane from the light emitting face of the light guide plate is used for liquid crystal back light, a panel meter, a display lamp, a plane light emitting switch or the like. With respect to lamps used as one type of light sources, it is required to design the lamps as a thin type in connection with the thickness of the light guide plate, and thus it is general to use a lamp constructed by providing a light emitting element to a thin reflection case having a front opening. For example, Japanese laid-open patent publication number Hei 8-264842 describes a lamp shown in FIG. 3. This lamp 120 is constructed by a synthetic resin reflection case 100 including an upper wall inner face 101 and a lower wall inner face 102 disposed to confront each other at a relatively small interval, right and left side wall inner faces 103 disposed to confront each other at a relatively large interval, a back wall inner face 104, a recess portion 105 surrounded by the inner faces 101 to 104, and a front opening 106. In this construction, a light emitting element 110 is provided to the back wall inner face 104, and the electrodes of the light emitting element 110 are connected to leads 112 provided to the reflection case 100.
Furthermore, as shown in FIGS. 4A and 4B, Japanese laid-open patent publication number 2004-193537 describes a lamp 130 which is constructed by providing a projecting portion 111 (hatched portion in FIG. 4A) at the lower side of a recess portion 105 and a front opening 106, stepwise lowering the center portion in the width direction of a lower wall inner face 102 so as to form an inner wall face 107, and continuously forming an inner wall face 108 so that the inner wall face 108 is inclined from the lower wall inner face 102 to the inner wall face 107 at a predetermined angle as shown in FIGS. 4A and 4B. This publication describes that the “predetermined angle” of the inner wall face 108 is any angle at which the inner wall face 108 is neither parallel nor perpendicular to the lower wall inner face 102 and the inner wall face 107 and light from the light emitting element can be efficiently reflected in the frontward direction of the light emitting device. Accordingly, light output from the light emitting element 110 is immediately reflected in the direction to the principal face of the light emitting device by the inner wall face 108, so that the light take-out efficiency of the light emitting device can be enhanced.